Hydraulic piston devices cooperating with sliding potentiometers



C PISTON DEVICES COOPERATING WITH -SLIDING POTENTIOMETERS Filed Nov. 23, 1965 `ton opening,

United States Patent Oiitice 3,355,690 Patented Nov. 28, 1967 3,355,690 v HYDRAULIC PISTON DEVICES COOPERATING WITH SLIDING POTENTIOMETERS Leif Erik Srensen, 131 Ryesgade, Copenhagen, Denmark,

and Svend Djems, Nykobing Falster, Denmark; said Djerns assigner to said Srensen Filed Nov. 23, 1965, Ser. No. 509,297 4 Claims. (Cl. 338-39) ABSTRACT F THE DISCLOSURE A hydraulic piston device cooperating with a sliding potentiometer, comprising a metallic cylinder having a piston slidably disposed within said cylinder, said piston being attached to a piston rod which extends out from said cylinder, said piston and said piston rod together being provided with an axial bore, said bore having an inner wall, a potentiometer coil comprising a core having an outer winding thereon, said core being attached to a cylinder bottom in spaced relationship with said inner bore wall and extending into said axial bore, a potentiometer contact member connected to said piston, means pressing said contact member against said potentiometer coil, and means providing electrical connection between said contact member and the inner cylinder wall, said potentiometer coil having one end connected to a lead extending outside the cylinder in electrically insulated relationship therewith.

This invention relates to hydraulic piston device cooperating with a sliding potentiometer. Such a potentiometer may be used for example in connection with electronic remote control of the member operated by the hydraulic piston device or as an answering potentiometer in an electromechanical control device for the hydraulic piston device.

Hitherto such potentiometers have been arranged thereby that the coil or potentiometer resistor is attached to the outer side of the cylinder of the piston device whereas the tap or sliding contact is connected to the piston rod. Hydraulc piston devices of the kind concerned are, however, often used in exposed positions so that a strong mechanical protection of the potentiometer is required and also in many cases it is necessary to provide against inuences on the potentiometer of the weather conditions, for example of moist.

The object of the invention is to provide hydraulic piston device cooperating with a sliding potentiometer which is extremely simple, in which the potentiometer does not require special protection, and does not take up extra space.

In the new device this is achieved by the potentiometer coil being attached to the cylinder bottom extending through an opening in the piston into an axially extending bore in the piston rod, and the sliding contact of the potentiometer being connected to the piston. Hereby is obtained that the potentiometer is well protected within the cylinder itself without taking up extra space. Further the potentiometer is embedded in the hydraulic Huid, so that weather changes can not efect the potentiometer. The additional electric resistance due to the inavoidable thin iiuid film between the coil and the sliding contact will in practice be so slight that it is of no importance and at most requires an initial adjustment.

Further it may be advantageous that the piston is provided with at least one transverse bore open into the pisand that a potentiometer contact member is arranged in said bore urged towards the potentiometer coil by resilient means. Hereby a simple arrangement of the potentiometer contact member is obtained without special connecting members between the contact member and the piston being required and without the contact member hampering the piston travel.

In this case most advantageously the transverse bore extends to the outer side of the piston, and within the bore there is arranged two contact members which are by means of a spring inserted between them pressed inwardly against the potentiometer coil and outwards against the cylinder wall respectively so that the cylinder wall can serve as electrical connectionv to the sliding potentiometer contact.

Other aspects, objects and the several advantages of this invention will be apparent from a study of this disclosure, the accompanying drawing and the appended claims.

The drawing shows a schematic axial sectional view of a device that embodies the invention.

10 indicates a hydraulic cylinder comprising a cylinder wall 12, a cylinder bottom 14 and a cylinder top 16 provided with a stuffing box 18 for a piston rod 20. The piston rod 20 is attached to a piston 22 slidably arranged within the cylinder 10 and provided with a through center opening 24 continuing into an axial bore 26 in the piston rod 20 which bore 26 -is closed at the outer end, not shown, of the piston rod.

In the middle of the cylinder bottom 14 is a linear hollow potentiometer coil 28 provided with an outer winding 30 is attached.- The coil 28 has a length only slightly shorter than the inner length of the cylinder wall 12 and extends through the piston opening 24 into the bore 26 of the piston rod 20. The one end of the winding 30 is connected to a terminal 34 outside the cylinder bottom 14 by means of a lead 36 pressure-proof passed through the cylinder bottom 14, whereas the other end of the winding 30 is by means of a lead 36 extending through the inner of the coil 28 and pressure-proof passed through the cylinder bottom 14 connected to another terminal 38.

The piston 22 is provided with at least one transverse bore 40 extending between the cylinder outer face of the piston and the piston opening 24. In the drawing two such bores 40 are shown. In each bore 40 a first contact ball 42 is slidably arranged at the end of the bore 40 communicating with the piston opening 24 and a second contact ball 44 is slidably arranged at the end of the bore open towards the cylinder wall 12. A compression spring 46 is inserted between the two contact balls 42 and 44. Thus the contact ball 42 serving as a sliding potentiometer contact is pressed against the winding 30 of the potentiometer coil 28 and is by means of the spring electrically connected to the contact ball 44 pressed against the cylinder wall 12, which is provided with a terminal 48 thus electrically connected to the potentiometer contact ball 42. Depending on the use to be made of the potentiometer either the terminal 48 and one of the terminals 34 and 38 may be inserted in a single electrical circuit or the terminals 34 and 38 may be connected to a pole each of an electric power source and a control or checking voltage derived from the terminal 48.

It will be understood that this invention is susceptible to modifications in order to adapt it to different usages and conditions; and, accordingly, it is desired to comprehend such modifications within the invention as may fall within the scope ofthe appended claims.

We claim:

1. An hydraulic piston device cooperating with a sliding potentiometer, comprising a metallic cylinder provided with a cylinder bottom and a cylinder top and having an inner cylinder wall, a piston slidably disposed within said cylinder, a piston rod attached at one end to said piston' and extending out from said cylinder through said cylinder top, said piston having an end face facing said cylinder bottom, said piston and said piston rod together being provided with an axial bore extending from said end face into said piston rod said bore having an inner Wall, a potentiometer coil comprising a core and an outer Winding, said core being attached to said cylinder bottom in spaced relationship with said inner bore wall and extending into said axial bore, a potentiometer contact member connected to said piston, means pressing said contact member against said potentiometer coil, means providing electrical connection between said contact member and said inner cylinder wall, said potentiometer coil winding having two ends, one of said ends being connected to la lead extending outside the said cylinder electrically insulated therefrom.

2. An hydraulic piston device cooperating with a sliding potentiometer as defined in claim 1, said piston being prov-ided with a transverse bore open into said axial bore, said potentiometer contact member being slidably arranged in said transverse bore, said means being a pressure spring disposed Within said bore and adapted to press said contact member against said coil.

3. An hydraulic piston device cooperating with a sliding potentiometer as defined in claim 2, said piston having a circumferential side face, said transverse bore being open also at said side face, a second contact member being slidably arranged in said bore at the end thereof open at said side face, said compressions spring being inserted between said two contact members thereby pressing said potentiometer contact member against said coil and said second contact member against the inner side of said cylinder.

4. An hydraulic piston device cooperating with a sliding potentiometer, comprising a metallic cylinder provided with a cylinder bottom and a cylinder top, a piston slidably disposed within said cylinder, a piston rod attached to said piston and extending out from said cylinder through said cylinder top, said piston being provided with an axially extending center opening, said piston rod being provided with an axially extending bore open at one end into said center opening, closed at the other end and having an inner wall, a potentiometer coil comprising a core and an outer coil Winding, said core being attached to said cylinder bottom at the center thereof and extendingl axially of said cylinder through said center opening into said axial bore in spaced relationship to said Iinner wall, said piston having a circumferential side face, said piston being provided with a transverse bore extending from said side face to said center opening, a rst contact member being slidably arranged in said transverse bore at the end thereof open into said center opening, a second contact member being slidably arranged in said transverse bore at the end thereof open at said side face, a compression spring being inserted between said two contact members thereby pressing said first contact member against said coil and said second contact member against the inner face of said cylinder.

References Cited UNITED STATES PATENTS 2,070,376 2/1937 Sherwood 338-39 2,248,047 7/1941 Addy et al 338-39 2,911,606 1l/1959 Hoffman 338--42 3,018,457 l/l962 Clason 338-39 3,098,209 7/1963 Stevens 73-398 RICHARD M. WOOD, Primary Examiner.

W. D. BROOKS, Assistant Examiner. 

4. AN HYDRAULIC PISTON DEVICE COOPERATING WITH A SLIDING POTENTIOMETER, COMPRISING A METALLIC CYLINDER PROVIDED WITH A CYLINDER BOTTOM AND A CYLINDER TOP, A PISTON SLIDABLY DISPOSED WITHIN SAID CYLINDER, A PISTON ROD ATTACHED TO SAID PISTON AND EXTENDING OUT FROM SAID CYLINDER THROUGH SAID CYLINDER TOP, SAID PISTON BEING PROVIDED WITH AN AXIALLY EXTENDING CENTER OPENING, SAID PISTON ROD BEING PROVIDED WITH AN AXIALLY EXTENDING BORE OPEN AT ONE END INTO SAID CENTER OPENING, CLOSED AT THE OTHER END AND HAVING AN INNER WALL, A POTENTIOMETER COIL COMPRISING A CORE AND AN OUTER COIL WINDING, SAID CORE BEING ATTACHED TO SAID CYLINDER BOTTOM AT THE CENTER THEREOF AND EXTENDING AXIALLY OF SAID CYLINDER THROUGH SAID CENTER OPENING INTO SAID AXIAL BORE IN SPACED RELTAIONSHIP TO SAID INNER WALL, SAID PISTON HAVING A CIRCUMFERENTIAL SIDE FACE, SAID PISTON BEING PROVIDED WITH A TRANSVERSE BORE EXTENDING FROM SAID SIDE FACE TO SAID CENTER OPENING A FIRST CONTACT MEMBER BEING SLIDABLY ARRANGED IN SAID TRANSVERSE BORE AT THE END THEREOF OPEN INTO SAID CENTER OPENING, A SECOND CONTACT MEMBER BEING SLIDABLY ARRANGED IN SAID TRANSVERSE BORE AT THE END THEREOF OPEN AT SAID SIDE FACE, A COMPRESSION SPRING BEING INSERTED BETWEEN SAID TWO CONTACT MEMBERS THEREBY PRESSING SAID FIRST CONTACT MEMAGAINST THE INNER FACE OF SAID CYLINDER. 